The present invention generally relates to a method of defibrillating a heart with an implantable cardiac stimulation system. The present invention more particularly relates to such a method wherein a defibrillating stimulation pulse is applied simultaneously across a plurality of different chambers of the heart.
Implantable cardiac stimulation devices are well known in the art. Such devices may include, for example, implantable cardiac pacemakers and defibrillators. The devices are generally implanted in a pectoral region of the chest beneath the skin of a patient within what is known as a subcutaneous pocket. The implantable devices generally function in association with one or more electrode carrying leads which are implanted within the heart. The electrodes are usually positioned within the right side of the heart, either within the right ventricle or right atrium, or both, for making electrical contact with their respective heart chamber. Conductors within the leads couple the electrodes to the device to enable the device to sense cardiac electrical activity and deliver the desired therapy.
Traditionally, therapy delivery had been limited to the venous, or right side of the heart. The reason for this is that implanted electrodes can cause blood clot formation in some patients. If a blood clot were released arterially from the heart left side, as for example the left ventricle, it could pass directly to the brain potentially resulting in a paralyzing or fatal stroke. However, a blood clot released from the right heart, as from the right ventricle, would pass into the lungs where the filtering action of the lungs would prevent a fatal or debilitating embolism in the brain.
Recently, new lead structures and methods have been proposed and even practiced for delivering cardiac rhythm management therapy to the left heart. These lead structures and methods avoid direct electrode placement within the left atrium and left ventricle of the heart by lead implantation within the coronary sinus region of the heart. As used herein, the phrase xe2x80x9ccoronary sinus regionxe2x80x9d refers to the venous vasculature of the left ventricle, including any portions of the coronary sinus, great cardiac vein, left marginal vein, left posterior ventricular vein, middle cardiac vein, and/or small cardiac vein or any other cardiac vein accessible by the coronary sinus.
It has been demonstrated that electrodes placed in the coronary sinus region of the heart may be used for left atrial pacing, left ventricular pacing, or cardioversion and defibrillation. These advancements enable implantable cardiac stimulation devices to address the needs of a patient population with left ventricular dysfunction and/or congestive heart failure which would benefit from left heart side pacing, either alone or in conjunction with right heart side pacing (bi-chamber pacing), and/or defibrillation.
Cardiac leads intended for use in the left heart via the coronary sinus region are difficult to position due to the tortuous venous routes of the human anatomy. Moreover, to provide both pacing and defibrillation of both the left atrium and the left ventricle from the coronary sinus region with multiple leads employing the appropriate types of electrodes is extremely difficult given the space constrains to accommodate multiple leads in the coronary sinus region. Hence, such implants are too cumbersome, difficult, and time consuming to perform and would likely result in compromised performance or system malfunction.
Universal pacing and defibrillation systems, capable of pacing and defibrillating all four heart chambers of the heart would require numerous pacing and defibrillation electrodes to be employed within the heart and its coronary venous system. To implement such a universal pacing and defibrillation system utilizing current state of the art lead configuration approaches, an inordinate number of leads would be required. This would result in lengthy implant procedures and possibly more leads than the human anatomy is able to accommodate. An inordinate number of leads may also make it difficult to accurately locate each electrode at a most efficacious position within the heart.
Efforts to minimize the number of required leads could also be fraught with potential obstacles. Such an effort would most likely include loading a lead up with too many electrodes. While this would reduce the number of required leads, such a lead would be difficult to implant. More importantly, owing to the differences in physiology from one patient to another, such a lead would most likely not xe2x80x9cfitxe2x80x9d a large number of patients in terms of resulting efficacious electrode positioning.
Efforts to achieve a universal pacing and defibrillation system, if successful, could provide significant improved therapies. Coordinated right heart and left heart pacing therapies would be made possible. Further, improved defibrillation therapies would also be made possible. Such therapies could include improved defibrillation energy distribution within the heart and/or new and improved sequential defibrillation pulse techniques.
The present invention provides a method of providing defibrillation stimulation to a heart with an implantable cardiac stimulation system wherein the stimulation pulse is applied with electrode configurations to deliver the stimulation pulse simultaneously across a plurality of chambers of the heart.
In accordance with one aspect of the invention, the stimulation pulse is applied with a first electrode configuration between a first chamber of the heart and third and fourth chambers of the heart and simultaneously applied with a second electrode configuration between a second chamber of the heart and the third and fourth chambers of the heart, one of the chambers of the heart being the left ventricle. In accordance with this aspect of the present invention, the first chamber may be the right atrium, the second chamber may be the right ventricle, the third chamber may be the left atrium and the fourth chamber may be the left ventricle. Alternatively, the first chamber may be the right atrium, the second chamber may be the left atrium, the third chamber may be the right ventricle, and the fourth chamber may be the left ventricle.
In accordance with a further aspect of the present invention, the conductive case of the implantable device may be used as an electrode. For example, the stimulation pulse may be applied with a third electrode configuration between the case and either the first and second chambers or the third and fourth electrodes.
In accordance with another aspect of the present invention, the stimulation pulse may be applied between the left ventricle of the heart and the case while simultaneously applying the stimulation pulse between a further chamber other than the left ventricle and the case. The further chamber may be the right ventricle.
In accordance with further aspects of the present invention, a defibrillation electrode is placed in electrical contact with each of the four chambers of the heart, a first common connection is formed with a first plurality of the electrodes, a second common connection is formed with a second plurality of the electrodes, and the stimulation pulse is delivered between the first and second connections. The electrodes for the left atrium and left ventricle may be electrically contacted with the left atrium and left ventricle by placing the electrodes within the coronary sinus region of the heart adjacent those chambers.